Capacitor

A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator).

Parasitic capacitance
Parasitic capacitance, stray capacitance or self-capacitance (of an inductor), is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other. All actual circuit elements such as inductors, diodes, and transistors have internal capacitance, which can cause their behavior to depart from that of 'ideal' circuit elements. In addition, there is always non-zero capacitance between any two conductors, such as wires, PCB traces and stripboard tracks. This is less significant at frequencies below 10MHz, but makes the use of stripboard for prototyping high precision VCOs and filters unreliable.